This invention relates to heat exchangers and more particularly to heat exchangers utilizing double walled tubes to reduce the possibility of contact between the heating and the heated fluid.
It is normally desirable to separate heating and heated fluid in a heat exchanger and depending on the compatibility of the fluids the effort and expense expended to insure separation varies. Double walled tubes with grooves in one of the contacting walls have been proposed to be highly reliable. However, the tube to tube sheet joints are an area where the probability of leakage is high even when spaced apart tube sheets are utilized and the inner wall of the tube is seal welded to one tube sheet and the other wall is seal welded to the other tube sheet so that the space between the tube sheets should be readily available for inspection and/or repair.